4502 Insects. 



ordinary gemmiparous form already described. Moreover, so great 

 was the similarity of appearance between these two forms — true fe- 

 males and gemmiparous individuals — that they could be distinguished 

 only by an examination of their internal genitalia. Among the pro- 

 per females there were, besides those which were filled with eggs or 

 had already deposited them, other individuals in which the ovaries 

 were but feebly developed, or, at least, in which no mature eggs had 

 been formed. An opportunity was thereby afforded me to examine 

 the structural differences between the true ovaries and their quasi re- 

 presentatives, the bud-like processes. The true ovaries had their 

 usual well-known structure, multilocular tubes containing nucleated 

 cells, which are probably the undeveloped germs ; the bud-like pro- 

 cesses, on the other hand, consisted of a row of cell-masses, oval and 

 connected by a kind of peduncle, as described in detail in the pre- 

 ceding paper. These wide differences have, more than ever, persuaded 

 me of the morphological dissimilarity of these two kinds of repro- 

 ducing parts in this animal. It seems to me, then, that the real in- 

 trinsic difference between an ovum and a bud lies as deep as the 

 conditions of sex itself, notwithstanding the latter often has, as in the 

 present case for instance, some of the morphological characteristics 

 of the former. 



The appearance of sexless gemmiparous individuals in the terminal 

 brood would seem to indicate, moreover, that the conditions which 

 determine the appearance of individuals, usually exclusively male and 

 female, are not, perhaps, referable to the fact of this being the last 

 brood, but rather to relations of warmth and nutrition. This view is 

 rendered more probable by the fact of the variation in the number of 

 broods between the first and last, observed in the same species in 

 different years, ranging between seven, nine, eleven or more. More- 

 over, Kyber, as quoted already in the preceding paper, by nursing 

 continually in a warm room a collection of Aphis Dianthi, keeping 

 about them a summer temperature, succeeded in continuing uninter- 

 ruptedly the series of sexless or gemmiparous individuals for four 

 years. There are many other facts in insect life that indicate in like 

 manner some direct relation between temperature and nutriment and 

 definite sexual development. The subject is as important as it is in- 

 teresting in physiology, and these very animals will perhaps subserve 

 the successful study of the primary morphological conditions of sex. 



